package com.myproject.io.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

public class NioSelectServer {

    private static List<SocketChannel> channelList = new ArrayList<>();

    public static void main(String[] args) throws IOException {

        //创建NIO ServerSocketChannel
        ServerSocketChannel serverSocket = ServerSocketChannel.open();
        serverSocket.socket().bind(new InetSocketAddress("localhost",9000));
        //设置ServerSocketChannel为非阻塞
        serverSocket.configureBlocking(false);
        //打开Selector处理Channel，即创建epoll
        Selector selector = Selector.open();
        //把ServerSocketChennel注册到selector上，并且selector对客户端的accept连接操作感兴趣
        serverSocket.register(selector, SelectionKey.OP_ACCEPT);
        System.out.println("服务器："+serverSocket.getLocalAddress()+" 启动成功");
        while (true){
            //阻塞等待需要处理的事件发生
            selector.select();

            //获取selector中注册的全部事件的 SecletionKey实例
            Set<SelectionKey> selectionKeys = selector.selectedKeys();
            Iterator<SelectionKey> iterator = selectionKeys.iterator();

            //遍历SelectionKey对事件进行处理
            while (iterator.hasNext()){
                SelectionKey key = iterator.next();
                if (key.isAcceptable()){ //如果是OP_ACCEPT事件，则进行连接获取和事件注册

                    ServerSocketChannel server = (ServerSocketChannel) key.channel();
                    SocketChannel socketChannel = server.accept();
                    socketChannel.configureBlocking(false);
                    //这里只注册了读事件，如果需要给客户端发送数据可以注册写事件
                    socketChannel.register(selector,SelectionKey.OP_READ);
                    System.out.println("客户端："+socketChannel.getRemoteAddress()+" 连接成功");
                } else if (key.isReadable()){ //如果是OP_READ事件，则进行读取和打印
                    SocketChannel socketChannel = (SocketChannel) key.channel();
                    ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
                    int len = socketChannel.read(byteBuffer);
                    //如果有数据，把数据打印出来
                    if (len>0){
                        System.out.println("客户端："+socketChannel.getRemoteAddress()+" 发送消息："+new String(byteBuffer.array()));
                    } else if (len==-1){//如果客户端断开链接，关闭Socket
                        System.out.println("客户端："+socketChannel.getRemoteAddress()+" 断开连接");
                        //TODO 这一步很关键
                        socketChannel.close();
                    }
                }
            }
            //TODO 这一步也很关键
            iterator.remove();
        }


    }
}
